An upcoming book about imprisoned Illinois Gov. Rod Blagojevich says that he had said on undercover tape-recordings that he had heard that $25,000 in cash had been secretly channeled to Barack Obama for his 2004 U.S. Senate campaign, but that federal authorities did not deem the claim credible.

In the book, “Golden: How Rod Blagojevich Talked Himself Out of the Governor's Office and into Prison,” authors Jeff Coen and John Chase suggest Blagojevich was talking about an undisclosed payment that was secretly provided to Obama by convicted Chicago influence peddler Antoin "Tony" Rezko, The Chicago Tribune reports.

The book says that federal investigators pursued the claim, but ultimately gave it little credence. “Never was Blagojevich seen as a credible threat to the incoming president,” Coen and Chase, two Tribune reporters, say in the book.

The White House referred questions about the matter to the Obama campaign. Ben LaBolt, a campaign spokesman, told The Tribune that the claim “is preposterous and it is false.

“No such payment was ever offered or made, and there never has been any suggestion or question of it from anyone, except apparently by Rod Blagojevich," LaBolt said.

Federal authorities declined to comment to The Tribune about the investigation.

An attorney for Rezko, who is serving a 10 1/2-year sentence for trying to extort money from firms seeking state business or regulatory approval, dismissed the allegation. He said that Blagojevich's claim is “simply a fabrication and not true.”

“You must keep in mind that the source of this allegation is inherently unreliable and not credible,” said the attorney, Joseph J. Duffy.

Blagojevich's lawyer, Sheldon Sorosky, did not return calls from The Tribune. Another of his other attorneys, Lauren Kaeseberg, declined to comment.

The disclosure of Blagojevich’s comments comes as the president is locked in a tight re-election campaign with Republican Mitt Romney, the former Massachusetts governor, who has sought to link Obama’s Chicago connections to the city’s culture of political corruption, The Tribune reports.

Obama’s ties to Rezko were a constant issue in the 2008 campaign. Rezko and Obama were friends, and Rezko raised as much as $250,000 for Obama for the first three political offices he sought, The Tribune reports.

Obama, meanwhile, engaged in a real estate deal with Rezko in which Rezko’s wife bought the lot next to the home that the Obamas purchased in 2005, then sold the lot to the Obamas for less than she paid, The Tribune reports.

Obama later acknowledged that the real estate deal was a lapse in judgment.

Blagojevich's claim about the money was caught on a government recording that was not made public during either of his federal trials, Coen and Chase say.

The authors do not say who gave them the recordings, The Tribune reports.